The present invention relates to a composite material and method of manufacture, wherein the composite material employs the use of a cementitious foam as a laminate layer within a multi layer panel to achieve improved acoustical and surface durability for use as an acoustic panel.
Conventional composite acoustic panels comprise a number of components to achieve sufficient structural rigidity and sound absorption. Many conventional acoustic panels contain mineral wool, perlite, and newsprint as primary ingredients. Such ingredients are typically wet formed from aqueous slurries using an organic binder such as a starch. Mineral wool may be comprised of fibers of rock wool or basalt. Additionally, glass fibers in combination with the mineral wool or glass fibers alone may be utilized. Typically, the slurry may either be wet formed upon a continuous moving screen, within a mold or directly onto a scrim material. A typical composite acoustical panel may also include backing materials and facing materials. One typical backing material includes kraft paper and the facing material is typically a latex paint providing acoustic permeability with aesthetic appeal.
Acoustic panels with a fiberglass batting typically include a kraft paper backing laminated to one face of the fiberglass batt with latex paint applied to the another. The fiberglass batt essentially consists of a pre-cut blank or solid of randomly arranged glass fibers bound together with an organic binder. Unfortunately, such fiberglass battings tend to lack surface integrity and rigidity.
Acoustical panels containing starch, newsprint, mineral wool and perlite are bound together by the starch, which is highly water-soluble. Such acoustic panels containing starch as a binder are susceptible to atmospheric moisture since when starch is partially hydrolyzed it loses a portion of its ability bind the ingredients of the panel. Such susceptibility to humid conditions tends to lead to warping or sagging of the panel.
Therefore, there is a need for an acoustic ceiling panel having sufficient rigidity and resistance to sag in a moist atmosphere.
The present invention provides for an acoustically absorbent porous panel that is both rigid and resistant to sagging caused by moisture. The acoustically absorbent porous panel is comprised of at least two layers. The first layer is a facing layer formed from a cured aqueous foamed cementitious material. The foamed cementitious material comprises on a wet basis about 53 to 68% by weight cement, about 17% to about 48% by weight water, 0% to about 10% by weight calcium silicate, about 0.05 to 5% by weight fiber, and about 0.01 to 10% by weight surfactant. Acoustically absorbent panels have pores distributed within the cured material comprising about 75 to 95% by volume of the material. The second layer is a backing layer that is affixed to the facing layer.
Additionally, a process is provided for producing an acoustically absorbent porous panel by producing a foamed cementitious composition by the steps of: 1) aerating a foam cementitious mixture, comprised of between about 53% and about 68% by weight cement, between about 17% and about 48% by weight water, between 0% and about 10% by weight calcium silicate, between about 0.05% and about 5% by weight synthetic organic fibers and between about 0.01% to about 10% by weight surfactant, 2) applying the foamed cementitious composition to a backing composition, 3) then curing the composition on the backing.
The present invention provides for an acoustically absorbent porous panel comprising a facing layer formed from a cured aqueous foamed cementitious material. The cured aqueous foamed cementitious material is comprised of cement, fibers and surfactant. The cured aqueous foamed cementitious material also has a density between about 10 and 40 lb/ft3, a Hess rake finger scratch test result of at least 12, an indentation of less than 0.12 inches, a Noise Reduction Coefficient of at least 0.5, and a sag test result of less than 0.15 inches at 90% RH. Then a backing layer is affixed to the facing layer.